A variety of instruments have been developed for use in the monitoring and treatment of medical conditions. Many such instruments provide a physician with information regarding a patient's condition, as well as information concerning the nature and effectiveness of any treatment provided. Often, the accuracy and availability of this information is dependent upon the operability of the instrument itself.
As might be expected, however, it may be difficult for the physician to continuously monitor all of the information available from the instrument, let alone evaluate the operability of the instrument. This problem is compounded when a number of instruments are being used simultaneously in the treatment of the patient. The problem may become particularly acute in an emergency situation, when the physician's attention is primarily focused upon the patient.
To ensure that important information is promptly called to the physician's attention, conventional medical instruments often produce messages associated with various patient, treatment, or instrument events. These messages may be in a variety of different forms. For example, in addition to a visible display, an audible message or alarm will often be employed to communicate the desired information in the event the instrument is outside the physician's field of view.
One type of medical instrument that conventionally provides a user with some form of messages is the defibrillator/monitor. A monitor portion of the instrument typically monitors the electrical activity of the patient's heart via two or more electrodes attached to the patient. A defibrillator portion of the instrument is used to, for example, apply a relatively large pulse of electrical energy to the patient via a pair of electrodes, to terminate fibrillation of the heart. The instrument may also include a pacing section that applies smaller periodic pulses of current to the patient's heart to cause the heart to beat at some desired rate.
Reviewing the message capabilities of certain prior art defibrillator/monitors, a number of different defibrillator/monitors are manufactured by Physio-Control, assignee of the present application. One such instrument is the LIFEPAK 8 defibrillator/monitor. The LIFEPAK 8 instrument is constructed to provide the attending physician with a variety of different messages.
Some of these messages are produced to apprise the physician of the patient's condition. For example, information from the monitor portion of the instrument is used to generate messages indicating that the patient's heart rate has crossed preset thresholds. Other messages provide the physician with information regarding the treatment being administered to the patient. For example, the defibrillator portion of the instrument initiates messages identifying the amount of energy discharged to the patient by the defibrillator. Still other messages contain information about the operability of the instrument. For example, information from sensing circuits included in the instrument is used to generate messages reflecting the condition of the instrument's batteries and the general service condition of the device.
The messages produced by the LIFEPAK 8 defibrillator/monitor include some visible and some audible messages. The visible messages may be as simple as lit indication lights. Each of the different visible messages is generally produced by a separate display element or separate segment of a display. With such dedicated displays used, however, the complexity of the instrument's face panel increases with the number of different messages to be produced.
The audible messages produced by the LIFEPAK 8 defibrillator/monitor are simple tones. Although audible messages may be especially suitable for conveying information to a physician in an emergency setting, the use of audible messages is relatively limited in the LIFEPAK 8 product.
Another prior art defibrillator/monitor of interest is the LIFEPAK 200 instrument manufactured by Physio-Control. The LIFEPAK 200 defibrillator/monitor includes a liquid crystal display (LCD), which generates a variety of different visible messages. In that regard, operator messages prompt an operator regarding the proper use and operation of the instrument. The LCD also allows six different instrument condition messages to be displayed.
The instrument condition messages include a "service" message, indicating that a self-diagnostic program run by the instrument has detected some fault in instrument readiness. A "low battery" message indicates that battery voltage, as monitored by a simple comparator, has dropped below some preset threshold. A "no tape" message indicates that a sensor included in the instrument's cassette recorder has not detected the presence of a cassette tape. A "tape" message further indicates that another sensor has determined that a cassette loaded into the recorder is either jammed or at the end of the tape.
Several messages produced by the LIFEPAK 200 are a function of the impedance of the interface formed between the patient and a pair of electrodes coupled to the instrument, as measured by an impedance measurement circuit. In that regard, a "connect electrodes" message indicates that the impedance has exceeded a preset threshold, suggesting that the electrodes are not adequately attached to the patient. Similarly, a "motion detected" message indicates that variations in the impedance of the patient/electrode interface have been detected, reflecting some patient/electrode disturbance.
Along with the various visible messages described above, the LIFEPAK 200 instrument also produces coded audible tones to prompt the operator and alert the operator to the presence of the warning messages described above. Each of the visible and audible messages is produced as soon as the associated instrument condition is detected. The messages have fixed durations and are immediately replaced by any messages associated with subsequently detected conditions.
As will be appreciated, although the message scheme used by the LIFEPAK 200 generally works well, it may have certain limitations when a number of message conditions occur simultaneously or over a short interval of time. Because the scheme treats all messages the same, a message associated with a relatively important condition may be replaced almost immediately with a message of lesser importance, depending upon the time at which the various conditions are detected. Similarly, while the LIFEPAK 200 message scheme provides the user with a message when the associated condition is first detected, it does not remind the user of the continued presence of the condition.
In view of the preceding observations, it would be desirable to produce a medical instrument that is able to provide an operator with a wide variety of messages without requiring an unduly complex display arrangement. It would also be desirable to ensure that relatively important messages are recognized as such and called to the operator's attention promptly and in several different formats. Finally, it would be desirable to ensure that some indication of an ongoing condition can be provided to the operator, particularly when the condition is of relative importance.